This invention relates to an earth-working concave agricultural disc useful, for example, for plowing and harrowing, cutting through and mixing ground trash or crop residue, preparing seedbeds during primary and secondary tillage operations, land clearing and site preparation, and preparing roadbeds for highway.
A disc implement or rig usually includes at least one gang of concave or dished circular steel discs with tapered or beveled peripheral edges, all of the discs sharing a common axis. Such an implement is pulled over the earth by a tractor with the common axis of the disc gang at an angle of less than 90.degree. from the line of forward movement of the tractor. The discs, although tending to roll or rotate as they are pulled forward, penetrate into and break up the soil, the loose soil riding up and across the concave surfaces and turning over or inverting. When tillage is performed for agricultural purposes, the objective is usually to provide a favorable soil environment for the germination and growth of a given crop. Good soil tilth is most important. Ideally, the best tilth quality is achieved when the soil is broken up or pulverized into small pieces that allow free access to air and water.
By employing cutaway notches or recesses on the periphery of each disc, the trash cutting capabilities are improved. Notched discs have better penetration because of their reduced peripheral contact area and cut heavy trash more readily since they tend to pull it under instead of pushing it ahead. The penetrating capability diminishes, however, as the disc is used and the notches wear out. As the disc works the soil, its diameter reduces from loss of material due to friction and the notches gradually disappear.
In the past, tractors pulling disc implements usually could not travel at speeds higher than about three miles per hour, and at that relatively slow discing speed the soil could be satisfactorily tilled. However, with the advancement in tractor technology, new and higher horsepower tractors are now available that can pull disc implements at much greater speeds, for example as high as ten miles per hour. Prior agricultural discs suffer from a number of disadvantages and deficiencies which render them unsatisfactory for high speed earth cutting. When conventional discs are pulled at high speeds, the concavity of the discs causes the soil to be thrown outwardly to such an extent that the ground becomes unleveled, with alternate high ridges and wide deep furrows. Of course, this tilth condition or quality is entirely unsatisfactory. Moreover, the undesired soil throwing and accumulation gives rise to soil erosion.
Another problem that occurs when prior conventional discs are pulled at high speeds is that there is a tendency to plow at a depth less than intended. As the discing speed increases over three miles per hour, disc penetration becomes quite shallow. In the past this was remedied by increasing the vertical load, usually by adding weights to the rig. With a greater vertical force, the requisite penetration could be attained, even though the degree of tilth is still entirely unsatisfactory. Moreover, the additional weight increases the draft force required to pull the discs, resulting in wasteful energy consumption.
Another disadvantage of using supplemental weight to obtain the required penetration is that undesired soil compaction occurs. Of course, the greater the soil is compacted, the more difficult it is for seeds to germinate. In addition, compacted soil is hard to work with next time the field is tilled.
The present invention provides a circular, dished earth-cutting agricultural disc, with peripheral notches, which lends itself to high speed use and overcomes all of the above problems and shortcomings. At high discing speeds, the soil may be cultivated without excessive throwing thereof and the resultant formation of furrows with spaced interruptions of accumulated soil, as is common with prior discs. The notched disc of the present invention has improved penetration capability, requiring less vertical force to penetrate to a given desired depth, as a consequence of which less draft force must be pulled by the tractor, thus conserving energy. Furthermore, by needing less weight for penetration, there is less compaction of soil.
Moreover, and this advantage is present even at low discing speeds, the unique geometric configuration of the present disc achieves vigorous stirring and mixing of soil to an extent and at a depth not attainable with prior discs at any speed.
An additional advantage of the notched disc of the invention is that excellent penetrating capability is retained even as the peripheral notches wear out completely and the disc's diameter decreases to the bottoms of the notches. The disc, therefore, has a much longer functional life than any notched disc developed heretofore.